The present invention relates to the field of couplers for connecting optical fibers to optoelectronic components. More specifically, the invention relates to a housing which accommodates an optical fiber end, provided with a coupling end face, and an optoelectronic element. A coupling element made of an optically transmissive material is disposed in the housing between the end of the optical fiber and the optoelectronic element in order to reduce back-reflections.
In the context of the invention, the optoelectronic element should be understood as being a transmitter or a receiver. When electrically driven, the optoelectronic element in the form of a transmitter converts the electrical signals into optical signals that are transmitted in the form of light signals. On receiving optical signals, the optoelectronic element in the form of a receiver converts these signals into corresponding electrical signals that can be tapped off at the output. In addition, an optical fiber is understood to be any apparatus for forwarding an optical signal with spatial limitation, in particular preformed optical fibers and so-called waveguides.
For optical data transmission at a high bit rate between an optoelectronic transmitter and an optoelectronic receiver, it is essential that back-reflections to the optoelectronic transmitter do not exceed a particular limit value defined in standards, in order to ensure fault-free operation of the optoelectronic transmitter.
In a known coupling configuration, the optical fiber, whose end is held in a plug, is in physical contact with the coupling element. That side of the coupling element that faces the optoelectronic element has a surface region that reduces back-reflections. In this context, the coupling element is in the form of an optical fiber portion whose axial extent is many times greater than its diameter. The optical fiber portion is held in a plug connector. That end of the optical fiber portion which faces the coupling end face ends at a first rounded end face of the plug connector, while that end of the optical fiber portion which faces the optoelectronic element ends at a second plug connector end face provided with a ground bevel. The coupling housing has a housing block which accommodates the optoelectronic element and to which a plug sleeve for holding the plug and the plug connector is attached. The plug sleeve is of a comparatively long axial configuration, in order to ensure that both the plug and the plug connector are held securely (see U.S. Pat. No. 5,937,122).
It is accordingly an object of the invention to provide a coupling configuration that overcomes the above-mentioned disadvantages of the prior art devices, in which a coupling housing is short and simple to produce.
With the foregoing and other objects in view there is provided, in accordance with the invention, a coupling configuration. The coupling configuration is formed of a coupling housing having a first region for accommodating an end of an optical fiber and a second region for accommodating an optoelectronic element. A coupling element made of an optically transmissive material is disposed in the coupling housing between the first region for accommodating the end of the optical fiber and the second region for accommodating the optoelectronic element. The coupling element is to be in physical contact with a coupling end face of the optical fiber when the optical fiber is inserted in the coupling housing. The coupling element has a side with a surface region which reduces back-reflections and the side faces the second region accommodating the optoelectronic element. The coupling element has a lens shape and is held directly in the coupling housing, and the coupling element couples the optical fiber to the optoelectronic element.
In accordance with the invention, the object is achieved in that the coupling element is of a lens-like configuration and is held directly in the coupling housing.
An essential advantage of the novel coupling configuration is that the axial extent of the lens-like coupling element is the same size as, or is even smaller than, its diameter required for optical coupling. This allows the coupling configuration overall to be shortened axially.
For simple mounting of the coupling element in the coupling housing and for simple alignment of the optical fiber, of the coupling element and of the optoelectronic element with respect to one another, it is advantageous for the coupling element to be in the form of a ball. The rotational symmetry of the ball results in that, irrespective of its axis position, it always has a spherical contact surface for reliable physical contact with the coupling end face of the optical fiber, and always has a spherical surface region on the side associated with the optoelectronic element. The spherical surface region ensures that the reflected light component is radiated back to the transmitter only to a very small degree.
A particularly simple and economical embodiment of the novel coupling configuration can be produced by forming the coupling element as an integral component of the housing. Therefore, for example, the coupling element can be produced as an integral part of the coupling housing in a joint injection-molding process. In this case, that side of the coupling element which faces the optoelectronic element may also have a ground bevel.
A particularly short physical form is possible, as an alternative to the embodiments described above, as a result of the coupling element being in the form of a plane-parallel plate whose side facing the optoelectronic element has a reflection-reducing coating and which is held directly in the coupling housing.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a coupling configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.